Jan 08, 2008

Del. County Develops Plan to Power Wastewater Plant with Grease

Project would use restaurant grease to produce electricity

Delaware’s Kent County is in the midst of a $15 million project that could use restaurant grease to produce the electricity needed to power the county's wastewater treatment plant near Frederica, according to The News Journal.

If the grease-to-energy system works, the result could be big savings for taxpayers.

"Our electric bill costs $70,000 a month," said Hans Medlarz, the county engineer and public works chief. "We think we could reduce that bill by 90%. That's our estimate going in."

The county has been researching the project for two years, Medlarz told the paper, mainly to determine how to set up a small wind farm as a backup to the grease-to-energy process. He estimated it could take four more years to put the plan into full effect.

"We're looking for a way to keep costs down and do a positive thing for the environment," Levy Court Commissioner Bradley S. Eaby said. Levy and Commissioner Richard E. Ennis are the primary overseers of the project, the newspaper reported.

"It would be a two-pronged project," Eaby said. "One prong would be the grease energy, and the second prong is wind or solar energy. But we're focusing on wind at the moment. That seems like a viable option."

Medlarz says only about $60,000 had been spent so far, although Levy Court has authorized expenditures of up to $250,000.

The technology used in the grease-to-energy process is well established. The grease would be converted to methane gas, which would be used to produce electricity—possibly as much as 5 megawatts, the daily amount needed to run the wastewater treatment plant, according to the newspaper.

"It's not a new technology," Medlarz said. "You produce the methane gas, collect it, use it as a heat source to generate steam, and the steam turns a turbine that generates electricity."

The gas would be a waste product of anaerobic digestion, a process in which bacteria eat away at fats, oils, grease and other organic solids stored in concrete tanks--the same process most wastewater treatment plants use to break down solids filtered out of sewage.

According to Medlarz, the county would recruit a private company to convert the methane gas to electricity, as well as operate the wind turbines and invest $12 million toward startup costs of $15 million. It would also receive a long-term deal to sell the electricity to the county, the paper reported.

"They are taking the raw resources, the wind and the methane, and turning them into electricity, and then we buy that electricity from them," Medlarz said.

Currently hindering the project is the lack of grease the county faces.

The county's sanitation code requires restaurants, food processors, and hospital and school cafeterias to catch grease in traps before it enters the county's sewer lines, because large concentrations of organic solids like fats, oils, grease and carbohydrates clog sewer lines.

These places have their own deals with haulers who dispose of their grease. As a result, the county need 10 times the grease it currently receives to make the project practical, the paper reported.

Medlarz has proposed a solution--a sanitation code amendment that would allow Kent County to go into nearby counties in search of grease.

"We'll be looking for other industries and talking to haulers, trying to increase our radius," Medlarz said. "Right now, I can operate only in Kent County."

The county hopes to emulate the success of Riverside, Calif., a city of about 300,000 that launched its Grease to Gas to Power Project in April 2005, according to the paper.

"We have processed over 13 million gallons of grease wastewater since March 27, 2006, with no harmful or deleterious effects to our wastewater treatment plant," Regan Bailey, wastewater operations manager for Riverside's public works department, told the paper in a recent e-mail.

The shortage of grease is not the only obstacle facing Kent County. The county has yet to determine how high it needs to build its backup windmill, the paper reported.

Medlarz said data collected from a tower 100 ft appears close to providing the necessary wind power.

Currently, the county plans to use two wind turbines and two anaerobic digesters. If the grease supply falls short, the county could possibly put in an additional wind turbine or two.

Because of the towers' proximity to Dover Air Force Base, several government agencies--including the Air Force, the Federal Aviation Administration and the federal Environmental Protection Agency--would have to approve the wind farm, according to the paper.